This invention relates generally to glass fibers and, more particularly, to solid optical fibers and glass capillaries coated with high temperature, high strength materials.
Glass fibers are more routinely used for a variety of applications. For example, in fiber optics, glass optical fibers are used to transmit voice, information or data signals in the form of light. These optical fibers include a silica core surrounded by a silica cladding having a lower index of refraction and typically have a diameter of about 125 microns, although somewhat larger and somewhat smaller diameter fibers have also been utilized. These fibers are usually coated with polymeric materials to protect the glass surface from abrasion and to facilitate their handling. These polymeric materials cannot withstand continuous exposure to temperatures in excess of from about 200.degree. C. to about 300.degree. C. In those applications requiring exposure to higher temperatures, the fibers have been coated with metal by a dip coating process. See U.S. Pat. No. 4,432,606, issued Feb. 2, 1984. The metal coating has been applied by a dip coating process and is satisfactory for applications wherein the coated fiber is exposed to temperatures of up to about 500.degree. C.
Glass capillaries are used in gas chromatography. These capillaries too are of a relatively small diameter and in the application noted above must withstand corrosive environments and temperatures in excess of 300.degree. C. In addition, the capillaries must have high strength--they must be able to be wrapped on a drum of finite diameter without breaking. One type of small diameter capillary is drawn from a large diameter tube to reduce its cross-section and the reduced cross-section capillary is coated with a polymeric material to increase its strength and facilitate its being wrapped on a drum. Similar to the polymer coated optical fibers noted above, the resultant capillaries cannot withstand continuous exposure to temperatures in excess of about 300.degree. C. Thus, their utility is limited.